COATED BODY WHEREIN THE COATING SCHEME INCLUDES A COATING LAYER OF TiAl2O3 AND METHOD OF MAKING THE SAME

ABSTRACT

A coated cutting insert and a method for making the same. The coated cutting insert has a substrate with a substrate surface. There is a backing coating scheme on the substrate surface, and a TiAl 2 O 3  coating layer wherein the TiAl 2 O 3  coating layer is deposited using chemical vapor deposition from a gaseous composition including AiCl 3 , H 2 , TiCl 4 , CO 2  and HCl.

CROSS REFERENCE TO EARLIER APPLICATION

This patent application is a divisional patent application which claims the benefit under the United States Patent Laws (35 USC 120) of co-pending U.S. patent application Ser. No. 14/207,828, filed Mar. 13, 2014 to Zhenyu Liu et al. for COATED BODY WHEREIN THE COATING SCHEME INCLUDES A COATING LAYER of TiAl₂O₃ AND METHOD OF MAKING THE SAME, which claims the benefit under the United States Patent Statute (Title 35 United States Code) including Section 119(e) of provisional U.S. patent application Ser. No. 61/804,007 filed Mar. 21, 2013 to Zhenyu Liu et al. for COATED BODY WHEREIN THE COATING SCHEME INCLUDES A COATING LAYER of TiAl₂O₃ AND METHOD OF MAKING THE SAME. Applicants hereby incorporate by reference herein the entirety of such provisional U.S. patent application Ser. No. 61/804,007 filed Mar. 21, 2013 to Zhenyu Liu et al. and applicants hereby incorporate by reference herein the entirety of such pending U.S. patent application Ser. No. 14/207,828 filed Mar. 13, 2014.

BACKGROUND OF THE INVENTION

The present invention pertains to a coated body (and method of making the same) wherein the coating scheme is applied by chemical vapor deposition (CVD), and especially coated cutting inserts that are useful in material removal applications such as, for example, machining, turning, and milling. More specifically, the present invention pertains to a coated body (and method of making the same), such as, for example, a coated cutting insert wherein the coating scheme includes a TiAl₂O₃ coating layer applied by CVD, and wherein the coated cutting insert exhibits acceptable properties including suitability in high performance cutting applications, high speed cutting applications, improved thermal resistance, and improved wear resistance.

Heretofore, coated bodies, such as, for example, coated cutting inserts, have been used in material removal applications. The coating layers typically comprise hard refractory materials that exhibit the properties of thermal resistance and/or wear resistance. One primary purpose of using a coating on a cutting insert has been to lengthen the useful life of the cutting insert. Exemplary such ones of these coating schemes are described in some of the following documents: article entitled “Titanium doped CVD alumina coatings”, Surface & Coatings Technology 203 (2008), pages 350-356 by Hochaer et al., article entitled “Doped CVD Al2O3 coatings for high performance cutting tools”, Surface & Coatings Technology 163-164 (2001), pages 181-188 by Kathrein et al., U.S. Pat. No. 4,180,400 to Smith et al., Japanese Published Patent Application No. 59-085860A to a PARTS OF CUTTING TOOL, U.S. Pat. No. 4,746,563 to Nakano, U.S. Pat. No. 6,660,371 to Westphal et al., and U.S. Pat. No. 7,326,461 to Sottke et al.

As is apparent from the above documents, many different coating schemes for a coated cutting insert have been used in the past. According to these documents, each one of these coating schemes provides certain advantages. Even though there have been coating schemes that are supposed to provide certain advantages, there has always remained a desire to continue to lengthen the useful life, as well as to improve the high performance cutting applications properties, high speed cutting applications properties, improved thermal resistance properties, and improved wear resistance properties of the coated cutting inserts. The desire to lengthen the useful life, as well as to improve the high performance cutting applications properties, high speed cutting applications properties, improved thermal resistance properties, and improved wear resistance properties is extant for coated cutting inserts.

Thus, it would be highly desirable to provide a coated cutting insert (and method of making the same, which is useful in material removal applications, with improved properties wherein the CVD coating comprises a coating scheme that includes a coating layer of TiAl₂O₃. Further, it would be highly desirable to provide a coated cutting insert (and method of making the same), which is useful in material removal applications, wherein the CVD coating comprises a coating scheme that includes a coating layer of TiAl₂O₃ and the cutting insert has a lengthened tool life, as well as exhibits improved performance characteristics. Still further, it would be highly desirable to provide a coated cutting insert (and method of making the same), which is useful in material removal applications, wherein the CVD coating comprises a coating scheme that includes a coating layer of TiAl₂O₃ and the cutting insert has a lengthened tool life, as well as exhibits acceptable properties including suitability in high performance cutting applications, high speed cutting applications, improved thermal resistance, and improved wear resistance.

SUMMARY OF THE INVENTION

In one form the invention is a coated cutting insert comprising a substrate having a substrate surface, a backing coating scheme on the substrate surface, and a TiAl₂O₃ coating layer wherein the TiAl₂O₃ coating layer is deposited using chemical vapor deposition from a gaseous composition including AlCl₃, H₂, TiCl₄, CO₂ and HCl.

In another form thereof, the invention is a method for making a coated cutting insert comprising the steps of: providing a substrate having a substrate surface; depositing by chemical vapor deposition a backing coating scheme on the substrate surface; and depositing by chemical vapor deposition a TiAl₂O₃ coating layer from a gaseous composition including AlCl₃, H₂, TiCl₄, CO₂ and HCl.

In still another form, the invention is a method for making a coated cutting insert comprising the steps of: providing a substrate having a substrate surface; depositing by chemical vapor deposition a backing coating scheme on the substrate surface; and depositing by chemical vapor deposition a TiAl₂O₃-aluminum oxide coating scheme comprising alternating coating layers of a TiAl₂O₃ coating layer deposited using chemical vapor deposition from a gaseous composition including AlCl₃, H₂, TiCl₄, CO₂ and HCl and an aluminum oxide coating layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings that form a part of this patent application:

FIG. 1 is an isometric view of a specific embodiment of a coated cutting insert of the invention with a portion of the coating scheme removed to expose the substrate;

FIG. 2 is a schematic cross-sectional view of the specific coating scheme that comprises the specific example of cutting insert R1 in Table 5;

FIG. 3 is a schematic cross-sectional view of the specific coating scheme that comprises the specific example of cutting insert R2 in Table 5;

FIG. 4 is a schematic cross-sectional view of the specific coating scheme that comprises the specific example of cutting insert R3 in Table 5;

FIG. 5 is a schematic cross-sectional view of the specific coating scheme that comprises the specific example of cutting insert R4 in Table 5;

FIG. 6 is a schematic cross-sectional view of one specific embodiment of a coating scheme that would be useful to use with the coated cutting insert of FIG. 1;

FIG. 7 is a schematic cross-sectional view of another specific embodiment of a coating scheme that would be suitable to use with the coated cutting insert of FIG. 1;

FIG. 8 is a schematic cross-sectional view of still another specific embodiment of a coating scheme that would be suitable to use with the coated cutting insert of FIG. 1;

FIG. 9 is a schematic cross-sectional view of yet another specific embodiment of a coating scheme that would be suitable to use with the coated cutting insert of FIG. 1;

FIG. 10 is a photomicrograph (having a scale of 10 micrometers) of the surface of a CVD Al₂O₃ coating layer;

FIG. 11 is a photomicrograph (having a scale of 10 micrometers) of the surface of a CVD TiAl₂O₃ coating layer of Example R3;

FIG. 12 is a photomicrograph (having a scale of 10 micrometers) of a cross-section of the rake face that is representative for cutting insert examples R1 through R4;

FIG. 13 is a photomicrograph (having a scale of 50 micrometers) of a cross-section of the corner for the cutting insert Example R1;

FIG. 14 is a photomicrograph (having a scale of 50 micrometers) of a cross-section of the corner for the cutting insert Example R4; and

FIG. 15 is a schematic cross-sectional view of the specific coating scheme that comprises the coating scheme of the KCP25 cutting insert used in the testing for Table 5.

DETAILED DESCRIPTION

FIG. 1 illustrates an embodiment of a coated cutting insert (which is one form of a coated body) that is generally designated as 20, and which is typically useful in conjunction with a cutting assembly for a chipforming material removal operation. In a chipforming material removal operation, the cutting insert engages a workpiece to remove material from a workpiece typically in the form of chips. A material removal operation that removes material from the workpiece in the form of chips typically is known by those skilled in the art as a chipforming material removal operation. The book Machine Shop Practice [Industrial Press Inc., New York, N.Y. (1981)] by Moltrecht presents at pages 199-204 a description, inter alia, of chip formation, as well as different kinds of chips (i.e., continuous chip, discontinuous chip, segmental chip). Moltrecht reads [in part] at pages 199-200, “When the cutting tool first makes contact with the metal, it compresses the metal ahead of the cutting edge. As the tool advances, the metal ahead of the cutting edge is stressed to the point where it will shear internally, causing the grains of the metal to deform and to flow plastically along a plane called the shear plane . . . . When the type of metal being cut is ductile, such as steel, the chip will come off in a continuous ribbon . . . ”. Moltrecht goes on to describe formation of a discontinuous chip and a segmented chip. As another example, the text found at pages 302-315 of the ASTE Tool Engineers Handbook, McGraw Hill Book Co., New York, N.Y. (1949) provides a lengthy description of chip formation in the metal cutting process. At page 303, the ASTE Handbook makes the clear connection between chip formation and machining operations such as turning, milling and drilling. The following patent documents discuss the formation of chips in a material removal operation: U.S. Pat. No. 5,709,907 to Battaglia et al. (assigned to Kennametal Inc.), U.S. Pat. No. 5,722,803 to Battaglia et al. (assigned to Kennametal Inc.), and U.S. Pat. No. 6,161,990 to Oles et al. (assigned to Kennametal Inc.).

Coated cutting insert 20 comprises a substrate 22. A portion of the coating of coated cutting insert 20 is removed so as to show substrate 22 in FIG. 1. The substrate 22 can be made from any one of a number of acceptable substrate materials. Coated cutting insert 20 has a flank surface 24 and a rake surface 26. The flank surface 24 and the rake surface 26 intersect to form a cutting edge 28 at the juncture thereof. There is a coating scheme 30 on the surface of the substrate 22. It should be appreciated that the coated cutting insert may exhibit geometries that are different from the geometry shown in FIG. 1

The substrate for each one of the specific embodiments can be selected from the same group of materials. In this regard, suitable materials for the substrate include, but are not limited to, cemented carbides (e.g., but not limited to, tungsten carbide-cobalt materials), ceramics (e.g., but not limited to, silicon nitride-based ceramics, SiAlON-based ceramics, titanium carbonitride-based ceramics, titanium diboride-based ceramics), cermets (e.g., but not limited to, cermets that have nickel-cobalt binder and a high level of titanium and could further include tungsten carbide and titanium carbide), and steels.

Applicants also contemplate that the substrate could exhibit gradient compositions, especially in the binder concentration, the carbonitride concentration and the carbide concentration. Exemplary substrates could include a cemented carbide substrate that presents a surface zone of binder enrichment or a cemented carbide substrate that exhibits a surface zone of binder depletion of solid solution carbide enrichment.

Other exemplary substrate materials are polycrystalline cubic boron nitride (PCBN) (exemplary PCBN materials include those with ceramic or metallic binder) and other superhard materials. The PCBN materials can be used in conjunction with cutting inserts in two basic ways. For one way, the PCBN inserts may be brazed to the cutting insert body. For the second way, the PCBN cutting inserts may be full top inserts.

It should be appreciated that applicants contemplate that prior to the deposition of the coating scheme the surface of the substrate may be treated so as to improve the adhesion of the coating scheme to the substrate. Exemplary pre-treatments include a process to remove or reduce the level of binder at the surface of the substrate. In the case of the cobalt cemented tungsten carbide substrate such a pre-treatment would remove cobalt from the surface of the substrate or treat the surface to improve the coating adhesion. Another exemplary pre-treatment would be a process that mechanically works the surface of the substrate so as to roughen the surface of the substrate making it ready to produce good coating adhesion.

It should be appreciated that applicants contemplate that in some instances the surface of the coating scheme may be subjected to a post-deposition treatment so as to improve performance and/or smoothness and/or adhesion. One exemplary treatment is the removal of asperities from the surface of the coating scheme so as to reduce or minimize any stress riser sites. Another exemplary treatment is to preferentially remove the coating (or a part of the coating layer) from selected areas of the cutting insert. A surface treatment typically reduces the tensile stresses or increases the compressive stresses in the coating layer(s). For example, PCT Patent Publication No. WO 02/077312 to Widia GmbH discloses shot blasting a coating (PVD or PCVD or CVD) to increase internal pressure stress or reduce internal tension stress in the outer coating layers.

Furthermore, it should be appreciated that to improve adhesion of the coating layers there may be provided microscopically rough interfaces between each of the coating layers. These microscopically rough interfaces can be generated by controlling the CVD (or moderate temperature chemical vapor deposition [MT-CVD]) parameters so as to promote high growth rates for the coating layers. High growth rates in CVD (including MT-CVD processes) processes may occur by the use of relatively high deposition temperatures and/or relatively high pressures. As another alternative to improve adhesion between coating layers, applicants contemplate that in the deposition process the composition can be gradually changed between adjacent layers so as to reduce the existence of a sharp compositional interface between adjacent coating layers.

In regard to the process to produce each one of the specific embodiments, it should be appreciated that for each one of the process steps, the pressure and the duration of the process step can vary so as to achieve the desired coating thickness.

Referring to the coating scheme illustrated in FIG. 2, which is the coating scheme for the specific Example R1 cutting insert used in the cutting tests, the results of which are set forth in Table 5—Test Results for Examples R1 through R4. There is shown a substrate that is a cemented (cobalt) tungsten carbide of the following composition: about 93 weight percent tungsten carbide and about 7 weight percent cobalt. The coating scheme includes a backing coating scheme that comprises a base coating layer of titanium nitride applied to the surface of the substrate. On the surface of the base coating layer of titanium nitride, there is deposited by a CVD technique a moderate temperature CVD (MT-CVD) titanium carbonitride coating layer. On the surface of the MT-CVD titanium carbonitride coating layer there is deposited by a CVD technique a titanium carbonitride coating layer (deposited at a higher temperature, e.g., about 950° C. to about 1000° C.) and which can be characterized as a HT-TiCN coating layer. On the surface of the HT-titanium carbonitride coating layer there is deposited by a CVD technique a titanium oxycarbonitride (or TiCNO coating layer) coating layer. The process parameters used to deposit these coatings layer of the backing coating scheme are set forth in Table 1—Processing Parameters for the Backing Coating Scheme wherein Table 1 sets forth ranges for the temperature (° C.), the pressure (torr), and the duration of the deposition of the coating layer (minutes). The gaseous components of the gaseous mixture are set forth in volume percent.

TABLE 1 Processing Parameters for the Backing Coating Layers Coating Temp. Pressure Duration layer (° C.) (Torr) (min) H₂ (%) N₂ (%) TiCl₄ (%) CO (%) CH₃CN (%) HCl (%) CH₄ (%) TiN  900~950° C. 100~150 20~100 80 19 1 — — — — MT-TiCN  800~850° C.  30~100 300~600  70 27.12 1.3 — 0.001 1.5 — HT-TiCN 950~1000° C. 100~150 30~150 78.8 16.7 0.8 — — — 3.7 TiOCN 950~1000° C. 200~500 10~100 77.5 17.7 1.1 1.1 — — 2.6 Table 1A below sets forth the specific temperature (° C.), the pressure (torr), and the duration of the deposition of the coating layer (minutes).

TABLE 1A Processing Parameters for the Backing Coating Layers Temp. Pressure Duration Coating Layer (° C.) (torr) (minutes) TiN 900° C. 120 torr 50 min. MT-TiCN 890° C. 76, 40 torr*  350 min.  HT-TiCN 985° C. 120 torr 60 min. TiOCN 985° C. 380 torr 30 min. *The MT-TiCN coating layer is deposited in two steps wherein one step is at 40 torr and the other step is at 40 torr.

Referring to Table 1, and Table 1A to the extent applicable, the column entitled “Coating Layer” refers to the specific coating layer of the backing coating scheme, the column entitled “Temp.” refers to the deposition temperature in degrees centigrade for the coating layer, the column entitled “Pressure” refers to the deposition pressure in torr, the column entitled “Duration” refers to the duration in minutes of the deposition of the coating layer, the next six columns refer to the specific gases that comprise the gaseous components of each step used to deposit the specific coating layer. The gas content is set forth in volume percent of the gaseous mixture.

Referring back to the coating scheme of FIG. 2, after completion of the deposition of the backing coating scheme, the next coating layer is of Al₂O₃ deposited using hydrogen sulfide (H₂S) in the deposition process on the surface of the TiCNO coating layer. The processing parameters used to deposit the Al₂O₃ with H₂S coating layer are set forth in Table 2—Processing Parameters for the Al₂O₃ Coating Layer Using H₂S wherein Table 2 sets forth ranges for the temperature (° C.), the pressure (torr), and the duration of the deposition of the coating layer (minutes). The gaseous components of the gaseous mixtures are set forth in volume percent.

TABLE 2 Processing Parameters for the Al₂O₃ Coating Layer Using H₂ S Coating Temp. Pressure Duration layer (° C.) (Torr) (min) AlCl_(s) (%) H₂ (%) CO₂ (%) HCl (%) H₂S (%) Al₂O₃ 950~1050° C. 50~100 60~300 1.8 91.2 3.2 3.5 0.3 Table 2A below sets forth the specific temperature (° C.), the pressure (torr), and the duration of the deposition of the coating layer (minutes).

TABLE 2A Processing Parameters for the Al₂O₃ Coating Layer Using H₂S Coating Temp. Pressure Duration Layer (° C.) (torr) (minutes) Al₂O₃ 985° C. 60 torr 120 min

Referring to Table 2, and to Table 2A to the extent applicable, the column entitled “Coating Layer” refers to the Al₂O₃ with H₂S coating layer, the column entitled “Temp.” refers to the deposition temperature in degrees centigrade for the coating layer, the column entitled “Pressure” refers to the deposition pressure in torr, the column entitled “Duration” refers to the duration in minutes of the deposition of the coating layer, the next five columns refer to the specific gases that comprise the gaseous components used to deposit the specific Al₂O₃ with H₂S coating layer. The gaseous components of the gaseous mixtures are set forth in volume percent.

The next coating layer is a TiAl₂O₃ coating layer deposited on the surface of the Al₂O₃ with H₂S coating layer, and the processing parameters used to deposit the TiAl₂O₃ coating layer are set forth in Table 4—Processing Parameters for the TiAl₂O₃ Coating Layer. Referring to Table 4, the column entitled “Coating Layer” refers to the TiAl₂O₃ coating layer, the column entitled “Temp.” refers to the deposition temperature in degrees centigrade for the coating layer, the column entitled “Pressure” refers to the deposition pressure in torr, the column entitled “Duration” refers to the duration in minutes of the deposition of the coating layer, the next five columns refer to the specific gases that comprise the gaseous components used to deposit the specific TiAl₂O₃ coating layer. The gaseous components of the gaseous mixtures are set forth in volume percent.

TABLE 4 Processing Parameters for the TiAl₂O₃ Coating Layer Coating Temp. Pressure Duration layer (° C.) (Torr) (min) AlCl_(s) (%) H₂ (%) CO₂ (%) HCl (%) TiCl₄ (%) TiAl₂O₃ 950~1050° C. 50~100 60~300 1.8 91.5 3.2 3.42 0.08 Table 4 sets forth ranges for the temperature (° C.), the pressure (torr), and the duration of the deposition of the coating layer (minutes). Table 4A below sets forth the specific temperature (° C.), the pressure (torr), and the duration of the deposition of the coating layer (minutes).

TABLE 4A Processing Parameters for the TiAl₂O₃ Coating Layer Coating Temp. Pressure Duration Layer (° C.) (torr) (minutes) TiAl₂O₃ 985° C. 60 torr 120 min.

Although a specific volume percent is set forth in Table 4, the content of the TiCl₄ can vary (see Table 7), as can be seen from the processing conditions, to result in different concentrations of titanium in the TiAl₂O₃ coating layer. This can include the introduction of TiCl₄ in a gradient manner so that the titanium concentration in the TiAl₂O₃ coating layer can exhibit a concentration gradient throughout the TiAl₂O₃ coating layer. Even though the specific process parameters do not use H₂S to deposit the TiAl₂O₃ coating layer, there is the expectation that H₂S could be used, and especially in lower flow rates such as, for example, less than about 20 percent of the conventional usage to deposit an Al₂O₃ coating layer.

There should be an appreciation that the step of depositing by chemical vapor deposition the TiAl₂O₃ coating layer can use a gaseous composition comprising about 0.5 to about 2.5 volume percent AlCl₃, about 82.5 to about 98 volume percent H₂, about 0.01 to about 2.0 volume percent TiCl₄, about 0.5 to about 5.0 volume percent CO₂ and about 0.2 to about 8.0 volume percent HCl.

The next coating layer is a Al₂O₃ with H₂S coating layer deposited on the surface of the TiAl₂O₃ coating layer. This Al₂O₃ with H₂S coating layer is deposited using the same processing parameters as set forth in Table 2 (and Table 2A)

The top two coatings layers are a TiCN coating layer deposited on the surface of the Al₂O₃ with H₂S coating layer and a TiN coating layer deposited on the surface of the TiCN coating layer. The processing parameters for the TiCN layer are like those for the HT-TiCN coating layer in Table 1 (and Table 1A) and the processing parameters for the TiN are like those for the TiN coating layer in Table 1 (and Table 1A).

FIG. 12 is a photomicrograph (having a scale of 10 micrometers) of a cross-section of the rake face that is typical for cutting insert examples R1 through R4. FIG. 13 is a photomicrograph (having a scale of 50 micrometers) of a cross-section of the corner for the cutting insert Example R1.

Referring to the coating scheme illustrated in FIG. 3, which is the coating scheme for the specific Example R2 cutting insert used in the cutting tests, the results of which are set forth in Table 5—Test Results for Examples R1 through R4. There is shown a substrate that is a cemented (cobalt) tungsten carbide of the following composition: about 93 weight percent tungsten carbide and about 7 weight percent cobalt. The coating scheme includes a backing coating scheme that comprises a base coating layer of titanium nitride applied to the surface of the substrate. On the surface of the base coating layer of titanium nitride, there is deposited by a CVD technique a moderate temperature CVD (MT-CVD) titanium carbonitride coating layer. On the surface of the MT-CVD titanium carbonitride coating layer there is deposited by a CVD technique a titanium carbonitride coating layer (deposited at a higher temperature, e.g., 950-1000° C.) and which can be characterized as a HT-TiCN coating layer. On the surface of the HT-titanium carbonitride coating layer there is deposited by a CVD technique a titanium oxycarbonitride (or TiCNO coating layer) coating layer. The process parameters used to deposit these coatings layer of the backing coating scheme are set forth in Table 1 and Table 1A.

The next coating layer is a Al₂O₃ with H₂S coating layer deposited on the surface of the TiCNO coating layer using the Parameters as set forth in Table 2 and Table 2A. The next coating layer is an Al₂O₃ without H₂S coating layer deposited on the surface of the Al₂O₃ with H₂S coating layer using the processing parameters as se forth in Table 3—Processing Parameters for the Al₂O₃ Coating Layer not Using H₂S. Referring to Table 3, the column entitled “Coating Layer” refers to the Al₂O₃ without H₂S coating layer, the column entitled “Temp.” refers to the deposition temperature in degrees centigrade for the coating layer, the column entitled “Pressure” refers to the deposition pressure in torr, the column entitled “Duration” refers to the duration in minutes of the deposition of the coating layer, the next four columns refer to the specific gases that comprise the gaseous components used to deposit the specific Al₂O₃ without H₂S coating layer. The gaseous components of the gaseous mixtures are set forth in volume percent.

TABLE 3 Processing Parameters for the Al₂O₃ Coating Layer Not Using H₂S Coating Temp. Pressure Duration layer (° C.) (Torr) (min) AlCl_(s) (%) H₂ (%) CO₂ (%) HCl (%) Al₂O₃ 950~1050° C. 50~100 10~60 1.8 91.5 3.2 3.5 Table 3 sets forth ranges for the temperature (° C.), the pressure (torr), and the duration of the deposition of the coating layer (minutes). Table 3A below sets forth the specific temperature (° C.), the pressure (torr), and the duration of the deposition of the coating layer (minutes).

TABLE 3A Processing Parameters for the Al₂O₃ Coating Layer not Using H₂S Coating Temp. Pressure Duration Layer (° C.) (torr) (minutes) Al₂O₃ 985° C. 60 torr 30 min.

The next coating layer is a TiAl₂O₃ coating layer deposited on the surface of the Al₂O₃ without H₂S coating layer. The process parameters to deposit the TiAl₂O₃ coating layer are set forth in Table 4 and Table 4A.

The next coating layer is a Al₂O₃ without H₂S coating layer deposited on the surface of the TiAl₂O₃ coating layer according to the process parameters in Table 3. An Al₂O₃ with H₂S coating layer is deposited on the surface of the Al₂O₃ without H₂S coating layer using the process parameters in Table 2.

The top two coatings layers are a TiCN coating layer deposited on the surface of the Al₂O₃ with H₂S coating layer and a TiN coating layer deposited on the surface of the TiCN coating layer. The processing parameters for the TiCN layer are like those for the HT-TiCN coating layer in Table 1 (and Table 1A) and the processing parameters for the TiN are like those for the TiN coating layer in Table 1 (and Table 1A). The thin TiN-top layer is deposited for wear indication and optical appearance. Further the TiN top layer can also function as sacrifice layer for post-coat wet-blasting to modify the stress situation in the coating layers.

Referring to the coating scheme illustrated in FIG. 4, which is the coating scheme for the specific Example R3 cutting insert used in the cutting tests, the results of which are set forth in Table 5—Test Results for Examples R1 through R4. There is shown a substrate that is a cemented (cobalt) tungsten carbide of the following composition: about 93 weight percent tungsten carbide and about 7 weight percent cobalt. The coating scheme for the Example R3 is like that for the Example R2, except for the introduction of the TiCl4 during the deposition of the TiAl₂O₃ coating layer. See Table 7.

Referring to the coating scheme illustrated in FIG. 5, which is the coating scheme for the specific Example R4 cutting insert used in the cutting tests, the results of which are set forth in Table 5—Test Results for Examples R1 through R4. There is shown a substrate that is a cemented (cobalt) tungsten carbide of the following composition: about 93 weight percent tungsten carbide and about 7 weight percent cobalt. The coating scheme for the Example R4 is like that for the Example R2, except for the introduction of the TiCl4 during the deposition of the TiAl₂O₃ coating layer. See Table 7. FIG. 14 is a photomicrograph (having a scale of 50 micrometers) of a cross-section of the corner for the cutting insert Example R4.

Table 5 sets forth the test results for metal cutting tests of Examples R1

TABLE 5 Metalcutting Test Results for Examples R1 through R4 Test conditions: 1000 sfm/0.012 ipr/0.08 doc 304.8 m/min/0.3048 mm/0.08 mm doc Continuous Turning Test/Lead Angle: ~5 Workpiece Material: 1045 Steel (C 45 DIN) Mean Relative Tool Tool Life Life NO. Tool Materials. Geometry (min) vs 1 1 KCP25 CNMG432 RN 12.0 2 TiAl₂O₃ R1 PostCoat Treated CNMG432 RN 11.6 96% 3 TiAl₂O₃ R2 PostCoat Treated CNMG432 RN 17.6 146% 4 TiAl₂O₃ R2 NO PostCoat CNMG432 RN 15.0 125% 5 TiAl₂O₃ R3 PostCoat Treated CNMG432 RN 13.8 115% 6 TiAl₂O₃ R4 PostCoat Treated CNMG432 RN 15.8 132% 7 TiAl₂O₃ R4 NO PostCoat CNMG432 RN 16.6 138% through R4 as compared against the KCP25 cutting insert. FIG. 15 describes the coating scheme of the KCP25 cutting insert used in the testing. The designation “NO Post Coat” means that the coated cutting insert was not subjected to a post-coating treatment. The designation “Post Coat Treated” means that the coated cutting insert was subjected to wet blasting with alumina grit after deposition of the coating scheme.

As is apparent from the test results, the Examples R2 through R4 exhibit improved tool life over the KCP25 cutting insert, which used the coating scheme as set forth in FIG. 15.

The thickness (in micrometers) for the Examples R1 through R4 are set

TABLE 6 Thickness (micrometers) of Coating Layers for Examples R1 through R4 Coating Thickness (μm) Layers TiAl₂O₃R1 TiAl₂O₃R2 TiAl₂O₃R3 TiAl₂O₃R4 TiN 0.6 0.7 0.5 0.5 MT-TiCN 10 9.0 9.6 9.2 HT-TiCN 0.9 1.3 0.9 0.8 Al₂O₃/ 7.7 7.3 11.2 8.8 TiAl₂O₃/ Al₂O₃ TiCN/TiN 2 2.6 2.5 2.3 Total 20.2 20.9 24.7 21.7 forth in Table 6 above. In reference to the thickness, the column identified as Al₂O₃/TiAl₂O₃/Al₂O₃ represents the total thickness (sum of the thicknesses) of the Al₂O₃ coating layers and the Ti Al₂O₃ coating layer.

It can therefore be appreciated that the coating scheme can have the following thickness parameters. The base titanium nitride coating layer has a thickness equal to between about 0.5 μm and about 0.7 μm. The MT-titanium carbonitride coating layer has a thickness equal to between about 9.2 μm and about 10 μm. The HT-titanium carbonitride coating layer has a thickness equal to between about 0.8 μm and about 1.3 μm. The thicknesses of the inner aluminum oxide coating layer deposited by chemical vapor deposition using hydrogen sulfide and the outer aluminum coating layer deposited by chemical vapor deposition using hydrogen sulfide and the TiAl₂O₃ coating layer added together is between about 7.3 μm and about 11.2 μm. The thickness of the exterior titanium-containing coating scheme is between about 2 μm and about 2.6 μm.

It can be further appreciated that the coating scheme can have the following thickness parameters. The base titanium nitride coating layer has a thickness equal to between about 0.05 μm and about 2.0 μm. The MT-titanium carbonitride coating layer has a thickness equal to between about 1.0 μm and about 25.0 μm. The HT-titanium carbonitride coating layer has a thickness equal to between about 0.05 μm and about 5.0 μm. The thickness of the inner aluminum oxide coating layer deposited by chemical vapor deposition using hydrogen sulfide and the TiAl₂O₃ coating layer added together is between about 0.5 μm and about 25.0 μm. The thickness of the exterior titanium carbonitride coating layer and the exterior titanium nitride layer added together is between about 0.5 μm and about 5.0 μm.

Referring to the coating schemes as set forth in FIGS. 6 through 9, the coating layers are self-explanatory. For each of the coating schemes of FIGS. 6-9, the backing coating scheme is deposited on the surface of the substrate. The backing coating scheme comprises a base coating layer of titanium nitride applied to the surface of the substrate. On the surface of the base coating layer of titanium nitride, there is deposited by a CVD technique a moderate temperature CVD (MT-CVD) titanium carbonitride coating layer. On the surface of the MT-CVD titanium carbonitride coating layer there is deposited by a CVD technique a titanium carbonitride coating layer (deposited at a higher temperature, e.g., 950-1000° C.) and which can be characterized as a HT-TiCN coating layer. On the surface of the HT-titanium carbonitride coating layer there is deposited by a CVD technique a titanium oxycarbonitride (or TiCNO coating layer) coating layer. The process parameters used to deposit these coatings layer of the backing coating scheme are set forth in Table 1—Processing Parameters for the Backing Coating Scheme.

For the coating scheme of FIG. 6, the TiAl₂O₃ coating layer is deposited on the surface of the TiCNO coating layer. The TiAl₂O₃ coating layer is typically deposited according to the process parameters of Table 4. The top two coatings layers are a TiCN coating layer deposited on the surface of the TiAl₂O₃ coating layer and a TiN coating layer deposited on the surface of the TiCN coating layer. The processing parameters for the TiCN layer are like those for the HT-TiCN coating layer in Table 1 and the processing parameters for the TiN are like those for the TiN coating layer in Table 1.

For the coating scheme of FIG. 7, the TiAl₂O₃ coating layer is deposited on the surface of the TiCNO coating layer. The TiAl₂O₃ coating layer is typically deposited according to the process parameters of Table 4. The Al₂O₃ coating layer is deposited on the surface of the TiAl₂O₃ coating layer. The specific process parameters are selected from those in Table 3 used to deposit the Al₂O₃ without H₂S coating layer and those process parameters in Table 2 to deposit the Al₂O₃ with H₂S coating layer. A TiAl₂O₃ coating layer is deposited on the surface of the Al₂O₃ coating layer. The TiAl₂O₃ coating layer is typically deposited according to the process parameters of Table 4. The top two coatings layers are a TiCN coating layer deposited on the surface of the TiAl₂O₃ coating layer and a TiN coating layer deposited on the surface of the TiCN coating layer. The processing parameters for the TiCN layer are like those for the HT-TiCN coating layer in Table 1 and the processing parameters for the TiN are like those for the TiN coating layer in Table 1.

There is the expectation that the use of the alternate coating layers of an Al₂O₃ coating layer and a TiAl₂O₃ coating layer can impact grain growth kinetics resulting in grain boundary, chemistry and interfacial structural differences as compared to a plurality of thin Al₂O₃ coating layers.

Further, there is the expectation that the grains may have different intragranular regions such as, for example, TiAl₂O₃ intragranular regions and Al₂O₃ intragranular regions. There can be a titanium concentration gradient in a grain from an intragranular region that has zero titanium to another intragranular region that has a maximum titanium content. There is also the expectation that there can be a titanium concentration gradient in a grain from an intragranular region that has zero titanium to another intragranular region that has a maximum titanium content and then still another intragranular region that has zero titanium. There is a suggestion that the grains (e.g., Ti Al₂O₃) can grow from early nucleation and keep growing until the Al₂O₃ region.

For the coating scheme of FIG. 8, the Al₂O₃ coating layer is deposited on the surface of the TiCNO coating layer. The specific process parameters are selected from those in Table 3 used to deposit the Al₂O₃ without H₂S coating layer and those process parameters in Table 2 to deposit the Al₂O₃ with H₂S coating layer. A TiAl₂O₃ coating layer is deposited on the surface of the Al₂O₃ coating layer. The TiAl₂O₃ coating layer is typically deposited according to the process parameters of Table 4. An Al₂O₃ coating layer is deposited on the surface of the TiAl₂O₃ coating layer, and a TiAl₂O₃ coating layer is deposited on the surface of the Al₂O₃ coating layer, and still another Al₂O₃ coating layer is deposited on the surface of the TiAl₂O₃ coating layer. The top two coatings layers are a TiCN coating layer deposited on the surface of the Al₂O₃ coating layer and a TiN coating layer deposited on the surface of the TiCN coating layer. The processing parameters for the TiCN layer are like those for the HT-TiCN coating layer in Table 1 and the processing parameters for the TiN are like those for the TiN coating layer in Table 1.

For the coating scheme of FIG. 9, the TiAl₂O₃ coating layer is deposited on the surface of the TiCNO coating layer. The TiAl₂O₃ coating layer is typically deposited according to the process parameters of Table 4. The Al₂O₃ coating layer is deposited on the surface of the TiAl₂O₃ coating layer. The specific process parameters are selected from those in Table 3 used to deposit the Al₂O₃ without H₂S coating layer and those process parameters in Table 2 to deposit the Al₂O₃ with H₂S coating layer. A TiAl₂O₃ coating layer is deposited on the surface of the Al₂O₃ coating layer. The TiAl₂O₃ coating layer is typically deposited according to the process parameters of Table 4. An Al₂O₃ coating layer is deposited on the surface of the TiAl₂O₃ coating layer. The top two coatings layers are a TiCN coating layer deposited on the surface of the TiAl₂O₃ coating layer and a TiN coating layer deposited on the surface of the TiCN coating layer. The processing parameters for the TiCN layer are like those for the HT-TiCN coating layer in Table 1 and the processing parameters for the TiN are like those for the TiN coating layer in Table 1.

There should be an appreciation that the above examples do not comprise all possible coating schemes that include the TiAl₂O₃ coating layer. The coating sequences can vary so that the TiAl₂O₃ coating layer is sandwiched between Al₂O₃ coating layers with an even additional variation including the Al₂O₃ with H₂S coating layer and the Al₂O₃ without H₂S coating layer.

FIGS. 10 and 11 compare the surface morphology of an Al₂O₃ coating layer and a TiAl₂O₃ coating layer, respectively. The grain morphology of the TiAl₂O₃ coating layer exhibits smaller grains and the larger grains are formed by the aggregated smaller, finer grains. The Al₂O₃ coating layer has sharper faceted grain structure.

Based upon SEM EDS analysis, the titanium content in the TiAl₂O₃ coating layers ranges between about 0.01 atomic percent and about 2 atomic percent.

In reference to the titanium content, in Examples R1 through R4 the content of TiCl₄ flow varies as shown by the Table 7 below.

TABLE 7 TiCl₄ Content in Gaseous Mixture Example TiCl₄ Flow Percentage (vol %) R1 0.08 R2 0.08 R3 0.12 R4 0.16

The patents and other documents identified herein are hereby incorporated by reference herein. Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or a practice of the invention disclosed herein. It is intended that the specification and examples are illustrative only and are not intended to be limiting on the scope of the invention. The true scope and spirit of the invention is indicated by the following claims. 

What is claimed is:
 1. A method for making a coating cutting insert comprising the steps of: providing a substrate having a substrate surface; depositing by chemical vapor deposition a backing coating scheme on the substrate surface; and depositing by chemical vapor deposition a TiAl₂O₃ coating layer from a gaseous composition including AlCl₃, H₂, TiCl₄, CO₂ and HCl.
 2. The method for making a coated cutting insert according to claim 1 wherein the step of depositing by chemical vapor deposition a TiAl₂O₃ coating layer occurs under the following parameters: a temperature between about 950° C. and about 1050° C., a pressure of between about 50 torr and about 100 torr, and a duration of between about 60 minutes and about 300 minutes.
 3. The method for making a coated cutting insert according to claim 1 wherein the step of depositing by chemical vapor deposition a TiAl₂O₃ coating layer occurs under the following parameters: a temperature equal to about 985° C., a pressure equal to about 60 torr, and a duration equal to about 120 minutes.
 4. The method for making a coated cutting insert according to claim 1 wherein the step of depositing by chemical vapor deposition a TiAl₂O₃ coating layer uses a gaseous composition comprising about 1.8 volume percent AlCl₃, about 91.5 volume percent H₂, about 0.08 volume percent TiCl₄, about 3.2 volume percent CO₂ and about 3.42 volume percent HCl.
 5. The method for making a coated cutting insert according to claim 1 wherein the step of depositing by chemical vapor deposition a TiAl₂O₃ coating layer uses a gaseous composition comprising about 0.5 to about 2.5 volume percent AlCl₃, about 82.5 to about 98 volume percent H₂, about 0.01 to about 2.0 volume percent TiCl₄, about 0.5 to about 5.0 volume percent CO₂ and about 0.2 to about 8.0 volume percent HCl.
 6. The method for making a coated cutting insert according to claim 1 further comprising a step of depositing on the TiAl₂O₃ coating layer by chemical vapor deposition an aluminum oxide coating layer.
 7. The method for making a coated cutting insert according to claim 6 wherein the step of depositing on the TiAl₂O₃ coating layer by chemical vapor deposition an aluminum oxide coating layer uses hydrogen sulfide, and occurs under the following parameters: a temperature between about 950° C. and about 1050° C., a pressure of between about 50 torr and about 100 torr, and a duration of between about 60 minutes and about 300 minutes.
 8. The method for making a coated cutting insert according to claim 6 wherein the step of depositing on the TiAl₂O₃ coating layer by chemical vapor deposition an aluminum oxide coating layer does not use hydrogen sulfide, and occurs under the following parameters: a temperature between about 950° C. and about 1050° C., a pressure of between about 50 torr and about 10 torr, and a duration of between about 10 minutes and about 60 minutes.
 9. A method for making a coated cutting insert comprising the steps of: providing a substrate having a substrate surface; depositing by chemical vapor deposition a backing coating scheme on the substrate surface; and depositing by chemical vapor deposition a TiAl₂O₃-aluminum oxide coating scheme comprising alternating coating layers of a TiAl₂O₃ coating layer deposited using chemical vapor deposition from a gaseous composition including AlCl₃, H₂, TiCl₄, CO₂ and HCl and an aluminum oxide coating layer.
 10. The method for making a coated cutting insert according to claim 9 wherein the aluminum oxide coating layer is deposited by chemical vapor deposition from a gaseous composition comprising AlCl₃, H₂, CO₂ and HCl and optionally H₂S. 